I use an old Futaba 8u. The great thing about it was that it was cheap because it was "old" technology, and it allows the usage of rf modules. This allows the entire rf section to be removed and replaced with 72MHz, 75MHz, or your favorite 2.4GHz flavor.

On a side note, it is sad to me that so many of these radios cost so much. There really is not all that much that goes into them. The programming is not terribly complicated. I know that there are some open source efforts out there as well.